Reimplemented dotdict iter{items,keys,values} to avoid using
__getitem__, by implementing them all in terms of iteritems (and
discarding the unnecessary key or value, as appropriate), instead of in
terms of iterkeys and performing a redundant lookup if the value is
required.
Minor documentation changes.
Support for parametric repeat of dfa machine
o peeking/chaining iterators support sent counter
o Cleaned up state context/extension support
o The cpppo.dfa repeat and cycle is accessed from the data artifact,
  and loops 'til the repeat is satisfied (or once, if None)
o Initial implementation of tnetstrings with Python2/3 support